Mechanical program control systems are well known, utilizing a rotary element in which a motor drives a stepping switch or a cam control switch during one, or more, or fractions of a revolution. The particular programming times of the respective program steps or cycles are controlled by cams formed on the circumference of a camming element. Time periods which are not utilized in some program steps can be obtained by leaving a cam disk blank, that is, not providing any cams thereon which merely causes rotation of the cam disk without, however, causing any switching events, or the like, to be controlled or commanded. Such programmed sequential timers or timing control units have the disadvantage that they are comparatively expensive to make, and are material-and-labor intensive. Their programming, and more particularly the change of programming, is difficult and possible only with considerable replacement of elements or cam disks, involving substantial disassembly and reassembly labor.